Thermal Transport Engineering in Hybrid Organic-Inorganic Perovskite Phononic Crystals.

Hybrid organic-inorganic perovskites have emerged as promising thermoelectric materials due to their attractive figure of merits. To further reduce their thermal conductances (G) and improve the thermoelectric efficiencies, fabrication of phononic crystals (PnCs) could be an effective approach. In this work, CH3NH3PbI3-based PnCs were developed and their thermal transports were engineered by optimizing the configurations of both basal bodies and scatterers. Our cross-scale simulations demonstrate that low relative G can be achieved in CH3NH3PbI3 PnCs with large scatterers but low-symmetric PnC lattices, basal bodies, and scatterers. Moreover, we discovered the increased disorder of CH3NH3+ cations from tetragonal to cubic transition significantly increases the phonon velocities and reverses the phonon transport from diffusive to quasi-ballistic, leading to an abnormal reduction of relative G. This work provides a new pathway for engineering thermal conductivity of hybrid perovskites and improving the performance of corresponding devices.